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排序方式: 共有365条查询结果,搜索用时 15 毫秒
71.
72.
Yu Cai Tianhou Zhang Alfred B. Anderson John C. Angus Lubomir N. Kostadinov Titus V. Albu 《Diamond and Related Materials》2006,15(11-12):1868
The ionization potentials and the electron affinities of doped diamond were calculated using B3LYP hybrid density functional theory and nanocrystalline cluster models, while taking into account the quantum confinement of the charge carriers. In many cases donor and acceptor levels were created in the middle of the gap between the conduction and valence bands. A possible explanation for the n-type behavior created by co-doping diamond films with boron and sulfur is given in terms of thermally activated electron donation from an SVS (V is vacancy) donor to a BB acceptor band. Both lie deep in the band gap. It is proposed that electrons in the BB acceptor band are mobile charge carriers. It is also proposed that the conversion of boron-doped diamond from p-type conductivity, with hole charge carriers in the top of the valence band, to n-type conductivity, following treatment in a deuterium plasma, may arise from formation of interstitial hydrogen donor levels and BnHm acceptor levels that create an acceptor band in which electrons are mobile. Again, both are deep in the band gap of pure diamond. In a prior attempt to explain this n-type behavior, BHn defects with unrelaxed structures were proposed to be shallow donors to the diamond conduction band. This paper shows that these defects become deep donors when their structures are optimized. Finally, defects created from vacancies with 1 to 4 H in them are shown to be deep donors to the diamond conduction band. 相似文献
73.
Angus Jeang 《国际生产研究杂志》2013,51(5):923-952
The need to remain competitive for survival in the current world market has led manufacturing sectors to consider the low cost and high quality of product and process design. Production of quality products at low cost in today's manufacturing industry requires simultaneous consideration of product design and process planning, particularly in the early stage of design and planning. During product design, parameter design determines the design target (design setting) and tolerance design determines design tolerance. During process design, the parameter design determines the process mean (process setting) and tolerance design determines process tolerance. This study provides a mathematical relationship to link the elements of design target, design tolerance, process mean and process tolerance in one equation. By following this equation, manufacturability for all possible combinations of product and process design can be ensured, which increases the flexibility of both product design and process planning. With this in mind, an analysis model that includes manufacturing cost and quality loss simultaneously has been developed to determine the optimal values of design tolerance, process mean and process tolerance. The proposed model provides a method of combining the optimization of parameter and tolerance design over product/process in the early stage of design. 相似文献
74.
Georgina K. Such Yan Yan Angus P. R. Johnston Sylvia T. Gunawan Frank Caruso 《Advanced materials (Deerfield Beach, Fla.)》2015,27(14):2278-2297
Over the last ten years, there has been considerable research interest in the development of polymeric carriers for biomedicine. Such delivery systems have the potential to significantly reduce side effects and increase the bioavailability of poorly soluble therapeutics. The design of carriers has relied on harnessing specific variations in biological conditions, such as pH or redox potential, and more recently, by incorporating specific peptide cleavage sites for enzymatic hydrolysis. Although much progress has been made in this field, the specificity of polymeric carriers is still limited when compared with their biological counterparts. To synthesize the next generation of carriers, it is important to consider the biological rationale for materials design. This requires a detailed understanding of the cellular microenvironments and how these can be harnessed for specific applications. In this review, several important physiological cues in the cellular microenvironments are outlined, with a focus on changes in pH, redox potential, and the types of enzymes present in specific regions. Furthermore, recent studies that use such biologically inspired triggers to design polymeric carriers are highlighted, focusing on applications in the field of therapeutic delivery. 相似文献
75.
Freeman Daniel; Pugh Katherine; Vorontsova Natasha; Antley Angus; Slater Mel 《Canadian Metallurgical Quarterly》2010,119(1):83
A key problem in studying a hypothesized spectrum of severity of delusional ideation is determining that ideas are unfounded. The first objective was to use virtual reality to validate groups of individuals with low, moderate, and high levels of unfounded persecutory ideation. The second objective was to investigate, drawing upon a cognitive model of persecutory delusions, whether clinical and nonclinical paranoia are associated with similar causal factors. Three groups (low paranoia, high nonclinical paranoia, persecutory delusions) of 30 participants were recruited. Levels of paranoia were tested using virtual reality. The groups were compared on assessments of anxiety, worry, interpersonal sensitivity, depression, anomalous perceptual experiences, reasoning, and history of traumatic events. Virtual reality was found to cause no side effects. Persecutory ideation in virtual reality significantly differed across the groups. For the clear majority of the theoretical factors there were dose–response relationships with levels of paranoia. This is consistent with the idea of a spectrum of paranoia in the general population. Persecutory ideation is clearly present outside of clinical groups and there is consistency across the paranoia spectrum in associations with important theoretical variables. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
76.
A dislocation model for simulating two-dimensional quasi-static crack propagation is presented. The crack and plastic flow
along slip planes are described using dislocation dipoles. A stationary crack can be modeled as well as a propagating crack
along a straight line inclined at an arbitrary angle to a free surface of a semi-infinite medium. Cracks are also allowed
to kink. A superdipole algorithm is introduced to save simulation time without loosing important information and necessary
geometric details. It reduces the number of dislocation dipoles on slip planes in the plastic wake. The paper gives results
on crack shapes for stationary and advancing cracks as well as it describes how the size of the plastic zone depends on crack
inclination angles. Results on stress intensity factors (SIF) are given using two different approaches as well as kinking
cracks are introduced and SIF at kinked crack tips are calculated. 相似文献
77.
In 4 experiments, the authors investigated accuracy of detecting a target among nontargets. In some experiments, the target was a second-order square of stationary lines on a background of downward-moving lines, and nontargets were second-order squares of upward-moving lines. In other experiments, target and nontarget squares and background were shades of gray. The principal comparison was between "new" and "old" object displays. In new-object displays, search items appeared abruptly and one might be a target. In old-object displays, search items appeared abruptly, and after a delay one might become a target. Search displays in both conditions terminated shortly after target onset. Except when target onset was associated with the sole luminance change in a display, targets were much better detected in new-than in old-object displays. It is suggested that object onsets elicit a brief stimulus-driven enhancement of attention to the new objects. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
78.
Anna-Clare Milazzo Grigore Moldovan Jason Lanman Liang Jin James C. Bouwer Stuart Klienfelder Steven T. Peltier Mark H. Ellisman Angus I. Kirkland Nguyen-Huu Xuong 《Ultramicroscopy》2010
The complete characterization of a novel direct detection device (DDD) camera for transmission electron microscopy is reported, for the first time at primary electron energies of 120 and 200 keV. Unlike a standard charge coupled device (CCD) camera, this device does not require a scintillator. The DDD transfers signal up to 65 lines/mm providing the basis for a high-performance platform for a new generation of wide field-of-view high-resolution cameras. An image of a thin section of virus particles is presented to illustrate the substantially improved performance of this sensor over current indirectly coupled CCD cameras. 相似文献
79.
Bioremediation of polycyclic aromatic hydrocarbons (PAH) in an aged coal-tar-contaminated soil using different in-vessel composting approaches 总被引:1,自引:0,他引:1
The biodegradation of 16 USEPA-listed PAHs (SigmaPAHs) during simulated in-vessel composting-bioremediation of an aged coal-tar-contaminated soil amended with fresh green waste compost (FGWC) collected from two landfill sites in the United Kingdom (UK) were studied over 56 days. The experimental design compared three constant temperature profiles (TC=38, 55 and 70 degrees C) with one variable temperature profile including treatment at 70 degrees C to comply with regulatory requirements (TP1). The highest disappearance of SigmaPAHs was observed in the soil amended with FGWC (53.2% and 48.1% SigmaPAHs disappearance in soil amended with FGWC-Site 1 and FGWC-Site 2, respectively) containing lower initial organic mater (TOM) (Initial TOM(FGWC-Site 1)=25.6+/-0.6%相似文献
80.
Five trained men were studied during 2 h of cycling exercise at 67% peak oxygen uptake at 20-22 degrees C to examine the effect of fluid ingestion on muscle metabolism. On one occasion, the subjects completed this exercise without fluid ingestion (NF) while on the other they ingested a volume of distilled deionized water that prevented loss of body mass (FR). No differences in oxygen uptake during exercise were observed between the two trials. Heart rate was lower (P < 0.01) throughout exercise when fluid was ingested, and rectal temperature after 2 h of exercise was lower (38.0 +/- 0.2 and 38.6 +/- 0.2 degrees C for FR and NF, respectively; P < 0.01), as was muscle (vastus lateralis) temperature (38.5 +/- 0.4 and 39.1 +/- 0.5 degrees C for FR and NF, respectively; P < 0.05). Resting muscle ATP, creatine phosphate, creatine, glycogen, and lactate levels were similar in the two trials, as were the postexercise ATP, creatine phosphate, and creatine levels. In contrast, muscle glycogen was higher (P < 0.05) and muscle lactate was lower (P < 0.05) after 2 h of exercise in FR compared with NF. Net muscle glycogen utilization during exercise was reduced by 16% when fluid was ingested (318 +/- 46 and 380 +/- 53 mmol/kg dry weight for FR and NF, respectively; P < 0.05). These results indicate that fluid ingestion reduces muscle glycogen use during prolonged exercise, which may account, in part, for the improved performance previously observed with fluid ingestion. 相似文献